Haptoglobin phenotype and prevalent coronary heart disease in the Framingham offspring cohort

Background: The haptoglobin (Hp) locus is polymorphic with two major alleles denoted 1 and 2. Several recent prospective longitudinal studies have demonstrated conflicting results regarding whether there is an increase or decrease in the relative risk of coronary heart disease (CHD) conferred on individuals homozygous for the haptoglobin 1 allele (Hp 1-1). Methods: We sought to examine the relationship between Hp type and prevalent coronary heart disease in a cross-sectional study from a large community-based cohort, the Framingham Heart Offspring Study (n=3273). Results: Overall we found no relation between Hp type and CHD prevalence. In secondary analyses we found a different pattern of Hp type and CHD prevalence by diabetes status. In nondiabetics, compared with Hp 1-1, Hp 2-1 (OR 1.71, 95% CI 1.03, 2.83) was associated with excess prevalence of CHD. In contrast in diabetic individuals we observed the opposite pattern; Hp 2-1 (OR 0.49, 95% CI 0.24, 0.99) and Hp 2-2 (OR 0.46, 95% CI 0.22, 0.96) were associated with diminished prevalence of CHD. Conclusions: These data are consistent with an interaction between Hp type and diabetes in the prevalence of CHD. These findings will need to be confirmed in other cohorts and in longitudinal studies.